I farmed these for about 7 hours. Saw 3 defender pop instead of destro (about 1/15). The 5 spawn location on the map are correct. There are 3 more pop location: 1 bottom-mid, 1 bottom-left and the mid location is 2 instead (1 on the low ground, and one on the hill). exactly 7 min spawn timer.
1/15 spawn ratio? Thank you for this info (I want the pet that the Defender drops).